A new UNICEF report says some 800,000 children have been forced from their homes in northeast Nigeria by an Islamic uprising, with many separated from their families and suffering abuse and emotional distress.

It says the number of refugee children has doubled in the past year. Children account for about half of all the 1.5 million made homeless in the Boko Haram conflict that has spilled across the borders of northeast Nigeria.

The report says children have become "deliberate targets," subjected to sexual abuse and forced marriage, kidnappings and killings.

Some children have become weapons, made to fight with armed groups and sometimes used as human bombs.

The number of children not attending primary school in Nigeria has increased from 8 million in 2007 to 10.5 million.